Fluidic oscillator

ABSTRACT

A fluidic oscillator is disclosed which incorporates a flexurally mounted jet pipe adapted to oscillate and discharge alternately into a pair of receivers. The jet pipe includes a pair of opposed reaction surfaces radially displaced from its rotational axis and aligned with a pair of driving ports. Output from the jet pipe receivers is amplified by a proportional fluid amplifier, and a negative feedback is provided whereby fluid output from the proportional amplifier is directed to the driving ports and issued therefrom as a pulsating jet stream to promote oscillation of the jet pipe. In an alternative embodiment, the proportional fluid amplifier is replaced by a digital fluid amplifier.

United States Patent Ringwall [63] Continuation-in-part of Ser. No.804,924,

March 6, 1969, abandoned. 5

[52] US. Cl ..l37/8l.5. 137/83 [51] Int. Cl. FlSc 3/12 [58] Field ofSearch ..137/8l.5, 82, 83; 235/201 51 Oct. 3, 1972 PrimaryExaminer-William R. Cline Attorney-Derek P. Lawrence, Thomas J. Bird,Jr., Lee H. Sachs, Frank L. Neuhauser, Oscar B. Waddell and Joseph B.Fonnan ABSTRACT A fluidic oscillator is disclosed which incorporates aflexurally mounted jet pipe adapted to oscillate and dischargealternately into a pair of receivers. The jet pipe includes a pair ofopposed reaction surfaces radially displaced from its rotational axisand aligned with a pair of driving ports. Output from the jet pipereceivers is amplified by a proportional fluid amplifier, and a negativefeedback is provided whereby fluid output from the proportionalamplifier is directed to [56] References Clted the driving ports andissued therefrom as a pulsating NI D STATES PATENTS jet stream topromote oscillation of the jet pipe. In an alternative embodiment, theproportional fluid ampli- 3,540,29O 1 H1970 Shlnn et a1 ..l37/8l.5 Xfier is replaced by a digita! fluid amplifier. 3,124,999 3/1964 Woodward..l37/83 X 3,275,015 9/1966 Meier 1 37/815 7 Claims, 4 Drawing Figuresin, v

/5 2 T 2 4 1 par/w" 20 Z4 f FLUIDIC OSCILLATOR This is acontinuation-in-part of application Ser. No. 804,924, filed Mar. 6, 1969now abandoned,,entitled Fluidic Oscillator, and assigned to the sameassignee as the present invention.

BACKGROUND OF THE INVENTION This invention relates to fluidic componentsand more particularly to a fluid oscillator capable of operating at apredetermined frequency with minimal sensitivity to supply pressure,temperature and vibration. The invention herein described was made inthe course of or under a contract, or a subcontract thereunder, with theUnited States Department of the Army.

Many fluidic circuits utilize an oscillator for generating a fixedfrequency reference against which a frequency generated elsewhere in thecircuit can be either directly or indirectly compared. For example, aprime mover such as a jet engine or turboshaft engine will have a shaftspeed limit beyond which sustained operation would be detrimental to theengine, and it becomes necessary to provide a governor system which willminimize overspeed operation. One such governor system comprises afluidic circuit which directly or indirectly compares a frequency signalproportional to shaft speed with a fluidic frequency signalrepresentative of the upper shaft speed limit, thus requiring areference frequency oscillator adaptable to the aircraft engineenvironment. The environment experienced by control components on anaircraft engine requires that fluidic components including theoscillator be relatively insensitive to changes in fluid supplypressure, temperature, and vibration as well as to small contaminants inthe fluid supply so that the weight and reliability penalties associatedwith devices such as pressure regulators and fluid filters can beminimized.

The prior art shows several oscillators adapted to provide a frequencyoutput which is relatively constant such as, for example, those shown inUS. Pat; No. 3,275,015, .I. H. Meier, Sept. 27, 1966, and US. Pat. No.3,333,596, S. Bottone, In, August 1967. Devices of this type are,however, subject to one or more of the effects described. For example,devices which use a vibrating reed or one leg of a tuning fork as aflapper to alternately open and close small bleed ports and thus varythe back pressure in a fluid line are contamination sensitive, supplypressure sensitive, and shock and vibration sensitive. Contaminationsensitivity results from the small limit on port size, supply pressuresensitivity results from the force which fluid issuing from a bleed portexerts on the vibrating flapper, this force being dependent upon thepressure of fluid supplied to the device, and shock and vibrationsensitivity is due to the displacement between the center of gravity andthe center of support.

OBJECTS OF THE INVENTION tion, shock and vibration insensitive.

BRIEF DESCRIPTION OF THE INVENTION Briefly stated, the inventioncomprises a jet pipe flexurally mounted to a base member for rotationaloscillation with respect thereto; the jet pipe is balanced to make itscenter of mass coincident with the center of rotation; the jet pipeincluding a jet nozzle for converting pressurized fluid to a fluid jetstream and a pair of opposed reaction surfaces radially spaced from therotational axis; the base member containing a pair of receivers adaptedto receive in varying proportions the jet stream issued from the jetnozzle and provide, either directly or indirectly, an output signal; andnegative feedback means for providing fluid flow from each of the outputmeans to a driving port aligned with a said reaction surface and locatedadjacent thereto, whereby each half cycle of oscillation of the jet pipewill result in fluid being recovered in a said receiver, provided to theoutput means and fed back to a driving port so as to reinforce thenatural oscillation of the jet pipe toward the opposite said receiver.

DESCRIPTION OF THE DRAWING While the specification concludes with claimsparticularly pointing out and distinctly claiming the invention, it willbe better understood by reference to the discussion below and theaccompanying drawing in which:

FIG. 1 is a partially schematic, partially plan view of a fluidicoscillator in accordance with this invention;

FIG. 2 is a section view taken along the line 2-2 of FIG. 1;

FIG. 3 is a fragmented section view taken along the line 3-3 of FIG. 1;and

FIG. 4 is a partially schematic, partially plan view of an alternativeembodiment of the fluidic oscillator shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a preferredform of the invention comprising a jet pipe device 10 which includes jetreceivers 12 and 14, a pair of oppositely disposed driving ports l6, l8,and a pair of reaction surfaces 20, 22 located on an extension 24 of jetpipe 26 and disposed between driving ports 20, 22. Jet receivers 12, 14are connected respectively through conduits or passageways (the twoterms are used interchangeably herein) 28, 30 to the control ports 32,34 to fluid amplifier 36. Fluid amplifier 36 is a proportional amplifierof the well known type having a power nozzle (shown schematically at38), a pair of receivers 40, 42 located downstream of the power nozzle38 and oppositely disposed with respect to the axis thereof, and thecontrol ports 32, 34 located on opposite sides of the axis of powernozzle 38 on a line intersecting therewith at a point between nozzle 38and receivers 40, 42. Thus, a relatively high velocity fluid streamissuing from nozzle 38 (which is supplied from source 44 via conduit 45)can be deflected by relatively small fluid streams issuing throughcontrol ports 32, 34 and directed toward one or both of receivers 40, 42in varying proportion to provide an output signal between conduits orpassageways 46, 48. A portion of the fluid flow which enters receivers40, 42 is fed back to driving ports 16,

18 respectively from output conduits 46, 48 via conduits 50, 52 anddirected to ports 16, 18 to impinge upon reaction surfaces 20, 22respectively and promote oscillation of jet pipe 26.

Referring now to FIGS. 1 3, jet pipe device comprises a base member 54,a collar 56 flexurally mounted to base member 54 by a torsional springdevice 55 such as that manufactured by Bendix Corporation generallyreferred to as a flexible pivot, and a member secured in collar 56 atright angles to the axis of rotation thereof, the member includingextension 24 and jet pipe 26. Jet pipe 26 includes an internalpassageway 57 which has its one terminus at a point near the axis ofrotation of collar 56 and terminates at its other end with jet nozzle58, which is located in the same plane as receivers 12, 14. Means forsupplying fluid to passageway 57 include a conduit '59 branching fromconduit 45 to a passage 62 in base member 54, a passage 64 extendingthrough the torsional spring device 55 to the interior of collar 56, ashort passage 68 extending from the cavity 70 in which torsional springdevice 55 is secured to an annulus 72 surrounding jet pipe 26, and apair of radial holes 74 extending through the wall of jet pipe 26 to theinterior thereof.

In addition to receivers l2, l4, and passageway 62 which are drilled orotherwise formed in base member 54, base member 54 includes a cavity 76in which the lower end of torsional spring device 55 is secured and apair of standards 78, 80 which extend upwardly to a point which is atapproximately the top of extension 24 and include the driving ports 16,18. Standards 78, 80 also include suitable passageway means 82, 84 whichare respectively connected with conduits 50, 52.

Operation of the oscillator can be described as follows. When nopressurized fluid is being supplied to the interior of jet pipe 26 frompressure source 44, jet pipe 26 will be oriented with respect toreceivers 12, 14 so as to favor discharge of its jet stream from nozzle58 into one or the other of receivers 12, 14. This state of the devicewill result from manufacturing tolerances providing a build-in bias toone or the other of receivers 12, 14. As soon as pressurized fluid issupplied to the interior of jet pipe 26, a fluid stream will issue fromjet nozzle 58 and be divided between receivers l2, 14 in a proportionwhich is dependent upon the actual static position of jet pipe 26. Oneor the other of receivers 12, 14 will receive a greater proportion ofthe fluid which will cause a pressure and flow differential betweencontrol ports 32, 34 of fluid amplifier 36. This differential pressureswill cause the simultaneously initiated power stream issuing from powernozzle 38 to be deflected toward one or the other of receivers 40, 42 ina proportion dependent upon the said pressure differential and providean output signal which appears as a pressure or flow differentialbetween conduits 46, 48. Part of the fluid flow appearing in conduit 46will be returned through conduit or passageway 50 and passageway 82 todriving port 16, and part of the flow appearing in output conduit orpassageway 48 will be similarly returned through conduit 52 andpassageway 84 to driving port 18. Fluid streams will issue from each ofports l6, 18 the relative momentum of the two fluid streams beingdependent upon the relative quantity of fluid being discharged intoconduits 46, 48. Thus, collar 56 will be subjected to a torque generatedby the fluid streams from ports l6, l8 impinging upon reaction surfaces20, 22, respectively and, because of physical coupling between reactionsurfaces 20, 22 and jet pipe 26, it will be urged from its initialposition to a position in which the opposite of receivers 12, 14 willpredominate over that which was favored initially. This will cause thedirection of the differential output of receivers 12, 14 to reverse andconsequently cause a reversal of the output signal between conduits 46,48, whereupon the feedback effect just described will take place inreverse to that initially described and move the jet pipe back to aposition approximating its initial position. The cycle described willthen repeat itself indefinitely to excite jet pipe 26 into anoscillation at the system natural frequency, which, if the fluidiccomponents and fluid lines are designed to have negligible capacitiveand inductive reactance, will be at the natural frequency of the springmass system comprising the torsional spring 55, collar 56, jet pipe 26,and extension Referring now to FIG. 4, an alternative form of theoscillator 10 of FIG. 1 is shown and generally labeled with the numeral100. The oscillator is identical to the oscillator 10 with the exceptionthat the proportional amplifier 36 is replaced with a digital fluidamplifier 102. The digital fluid amplifier 102 is of the well known typehaving a power nozzle (shown schematically at 104), a pair of receivers106, 108 located downstream of the power nozzle 104 and oppositelydisposed with respect to the axis thereof and control ports 110, 112located on opposite sides of the axis of the power nozzle 104. Thecontrol ports 110, 112 are located on a line intersecting the axis ofthe power nozzle 104 at a point between the nozzle 104 and the receivers106, 108. Thus, a relatively high velocity fluid stream issuing from thenozzle 104 (which is supplied from the source 44 via the conduit 45),can be deflected by relatively small fluid streams issuing through thecontrol ports 110, 112. In contrast to the proportional amplifier 36which provides a signal at the receivers 40, 42 in varying proportionsto the pressure of the fluid at the control ports 32 and 34 (and thusprovides an output signal between conduits 46 and 48 which varies inproportion to the input pressures), the digital amplifier 102 providesan output at either receiver 106 or 108 in response to an input at thecontrol ports 112 and 110, respectively. In other words, the outputsignal between conduits 46 and 48 becomes a square wave output asopposed to a sine wave (or some similar function).

Operation of the oscillator 100 is also very similar to that of theoscillator 10. Once again, manufacturing tolerances provide a built-inbias to one or the other of receivers 12, 14 from the jet pipe 26. Assoon as pressurized fluid is supplied to the interior of the jet pipe26, a fluid stream will issue from the jet nozzle 58 and will be dividedbetween receivers 12 and 14 in a proportion which is dependent upon theactual static position of the jet pipe 26. One or the other of thereceivers 12, 14 will receive a greater proportion of the fluid whichwill cause a pressure and flow differential between the control ports110, 112 of the fluid amplifier 102. This differential pressure willcause the simultaneously initiated power stream issuing from the powernozzle 104 to be deflected toward one or the other of the receivers 106,108. This results in an output signal which appears as a pressure orflow differential between conduits 46, 48.

returned through the conduit or passageway 50 and the passageway 82 tothe driving port 16; and part of the flow appearing in output conduit orpassageway 48 will be similarly returned through the conduit 52 and thepassageway 84 to the driving port 18. Fluid streams will issue from eachof the ports 16 and 18 with the relative momentum of the two fluidstreams being dependent upon the relative quantity of the fluid beingdischarged into the conduit 46 and 48.

Thus, the collar 56 will be subjected to a torque generated by the fluidstreams from the ports 16 and 18 impinging upon the reaction surfaces 20and 22, respectively, and because of the physical coupling between thereaction surfaces 20 and 22 and the jet pipe 26, the jet pipe 26 will beurged from its initial position to a position in which the opposite of Ithe receivers 12, 14 will predominate over that which was favoredinitially. This will cause the direction of the differential output ofreceivers 12 and 14 to reverse, and consequently, cause a reversal ofthe output signal between conduits 46 and 48. The feedback effectpreviously described willthen take place in reverse and will move thejet pipe 26 back to a position approximating its initial position. Thecycle described will then repeat itself indefinitely to excite the jetpipe 26 into an oscillation at the system natural frequency. X

Operation of the oscillator as described will be relatively insensitiveto contamination appearing in the fluid supplied from source 60 inasmuchas jet nozzle 58 and receivers 12, 14 can be constructed to have a sizesufficient to permit passage of most commonly encountered contaminants.Further, inasmuch as all interaction between the jet stream issuing fromnozzle 58 and the receivers 12, 14 will have force components parallelto the oscillating plane (i.e., that defined by the longitudinal axis ofjet pipe 26 and the axis of rotation of collar56), there will be notorque coupling between the jet pipe 26 and receivers 12, 14 tending todamp the oscillation. In this connection, it should also be noted thatif receivers 12, 14 were located adjacent the end 86 of jet pipe 26 inthe plane of oscillation (i.e., that plane normal to the axis ofrotation of collar 56) and jet nozzle 58 extended longitudinally throughthe end 86 of jet pipe 26, any interaction between nozzle 58 andreceivers 12, 14 would similarly be void of a damping effect upon theoscillation of jet pipe 26. This absence of damping or torque couplingbetween the active oscillating member and its output means operates torender the oscillator almost entirely independent of the pressuresupplied from source 60. This is in contrast to the result obtained withthe prior art devices incorporating a vibrating reed flapper or othersimilar device which alternately varies the area of bleed orifices froma pair of conduits containing pressurized fluid so as to superimpose acyclic pressure variation on a steady or do signal. In these lattermentioned devices, the interaction between the dc. signal and theoscillating member results in forces which tend to dampen the 6oscillation, the magnitude of the damping efi'ect being 5 dependent uponthe dc. level, which is in turn dependent upon the supply pressure ofthe active fluid.

Having thus described the invention, what is desired to be secured byLetters Patent is claimed below.

I claim:

1. A constant frequency fluidic oscillator which comprises A. ajet ipedevice comprising,

a base member a jet pipe flexurally mounted to said base member forrotational oscillation with respect thereto, said jet pipe includingmeans for supplying pressurized fluid to the interior thereof, a jetnozzle for converting the pressurized fluid to a fluid jet stream; and apair of opposed reaction surfaces radially spaced from the rotationalaxis thereof,

a pair of jet receivers formed in said base member and located thereinto be impinged upon by the said fluid jet stream, said receivers beinglocated on opposite sides of the longitudinal axis of said jet pipe whensaid jet pipe is at a mid-point of its oscillation, said jet pipe beingpositioned so as to favordischarge of its jet stream into one of saidpair of jet receivers when neither of the opposed reaction surfaces isbeing acted upon,

a pair of driving ports, each disposed adjacent one of said reactionsurfaces and spaced therefrom a distance sufficient to permit motion ofsaid reaction surfaces between said driving ports; and

means for supplying pressurized fluid to said jet B. output means forobtaining an output signal from said receivers; 4 w

C. negative feedback means for directing the output signal from a firstsaid jet receiver to the one of said driving ports which is coupledthrough a reaction surface on said jet'pipe to urge said jet pipe nozzleto a position in which the second said receiver will be impinged by saidjet stream; and

D. negative feedback means for directing the output signal from thesecond said jet receiver to the oppositeof said one driving port.

2. The fluidic oscillator recited in claim 1 wherein A. said outputmeans includes a proportional fluid amplifier having a power nozzle forconverting pressurized fluid to a fluid power stream, a pair of outputreceivers located downstream of said power nozzle and oppositelydisposed with respect to the axis thereof, and a pair of control portsoppositely disposed with respect to the axis of said power nozzle on aline intersecting therewith at a point between said power nozzle andsaid receivers,

passageway means connecting the first said jet receiver with one of saidcontrol ports, and

passageway means connecting the second said jet receiver with the otherof said control ports; and

B. said negative feedback means comprises said fluid amplifier, andpassageway means connecting a first said output receiver to the one ofsaid driving ports which is coupled through a reaction surface on saidjet pipe to urge said jet pipe to a position which will cause the signalfrom said output means to predominate in the second said outputreceiver, and passageway means for connecting the second said outputreceiver to the opposite of said one driving port.

3. The fluidic oscillator recited in claim 2 wherein said jet pipecomprises a collar flexurally mounted to said base member and having anaxis of rotation with respect thereto;

a hollow pipe extending from said axis of rotation in a direction normalthereto; and

a solid member extending in a direction opposite the said one directionand including at its end the said reaction surfaces.

4. The fluidic oscillator recited in claim 3 wherein the axis of saidjet nozzle is parallel to said axis of rotation.

5. The fluidic oscillator recited in claim 1 wherein A. said outputmeans includes a digital fluid amplifier having a power nozzle forconverting pressurized fluid to a fluid power stream, a pair of outputreceivers located downstream of said power nozzle and oppositelydisposed with respect to the axis thereof, and a pair of control portsoppositely disposed with respect to the axis of said power nozzle on aline intersecting therewith at a point between said power nozzle andsaid receivers, passageway means connecting the first said jet receiverwith one of said control ports, and passageway means connecting thesecond said jet receiver with the other of said control ports; and

B. said negative feedback means comprises said fluid amplifier, andpassageway means connecting a first said output receiver to the one ofsaid driving ports which is coupled through a reaction surface on saidjet pipe to urge said jet pipe to a position which will cause the signalfrom said output means to predominate in the second said outputreceiver, and

passageway means for connecting the second said output receiver to theopposite of said one driving port. 6. The fluidic oscillator recited inclaim 5 wherein said jet pipe comprises a collar flexurally mounted tosaid base member and having an axis of rotation with respect thereto;

a hollow pipe extending from said axis of rotation in a direction normalthereto; and

a solid member extending in a direction opposite the said one directionand including at its end the said reaction surfaces.

7. The fluidic oscillator recited in claim 6 wherein the axis of saidjet nozzle is parallel to said axis of rotation.

1. A constant frequency fluidic oscillator which comprises A. a jet pipedevice comprising, a base member a jet pipe flexurally mounted to saidbase member for rotational oscillation with respect thereto, said jetpipe including means for supplying pressurized fluid to the interiorthereof, a jet nozzle for converting the pressurized fluid to a fluidjet stream; and a pair of opposed reaction surfaces radially spaced fromthe rotational axis thereof, a pair of jet receivers formed in said basemember and located therein to be impinged upon by the said fluid jetstream, said receivers being located on opposite sides of thelongitudinal axis of said jet pipe when said jet pipe is at a mid-pointof its oscillation, said jet pipe being positioned so as to favordischarge of its jet stream into one of said pair of jet receivers whenneither of the opposed reaction surfaces is being acted upon, a pair ofdriving ports, each disposed adjacent one of said reaction surfaces andspaced therefrom a distance sufficient to permit motion of said reactionsurfaces between said driving ports; and means for supplying pressurizedfluid to said jet pipe; B. output means for obtaining an output signalfrom said receivers; C. negative feedback means for directing the outputsignal from a first said jet receiver to the one of said driving portswhich is coupled through a reaction surface on said jet pipe to urgesaid jet pipe nozzle to a position in which the second said receiverwill be impinged by said jet stream; and D. negative feedback means fordirecting the output signal from the second said jet receiver to theopposite of said one driving port.
 2. The fluidic oscillator recited inclaim 1 wherein A. said output means includes a proportional fluidamplifier having a power nozzle for converting pressurized fluid to afluid power stream, a pair of output receivers located downstream oFsaid power nozzle and oppositely disposed with respect to the axisthereof, and a pair of control ports oppositely disposed with respect tothe axis of said power nozzle on a line intersecting therewith at apoint between said power nozzle and said receivers, passageway meansconnecting the first said jet receiver with one of said control ports,and passageway means connecting the second said jet receiver with theother of said control ports; and B. said negative feedback meanscomprises said fluid amplifier, and passageway means connecting a firstsaid output receiver to the one of said driving ports which is coupledthrough a reaction surface on said jet pipe to urge said jet pipe to aposition which will cause the signal from said output means topredominate in the second said output receiver, and passageway means forconnecting the second said output receiver to the opposite of said onedriving port.
 3. The fluidic oscillator recited in claim 2 wherein saidjet pipe comprises a collar flexurally mounted to said base member andhaving an axis of rotation with respect thereto; a hollow pipe extendingfrom said axis of rotation in a direction normal thereto; and a solidmember extending in a direction opposite the said one direction andincluding at its end the said reaction surfaces.
 4. The fluidicoscillator recited in claim 3 wherein the axis of said jet nozzle isparallel to said axis of rotation.
 5. The fluidic oscillator recited inclaim 1 wherein A. said output means includes a digital fluid amplifierhaving a power nozzle for converting pressurized fluid to a fluid powerstream, a pair of output receivers located downstream of said powernozzle and oppositely disposed with respect to the axis thereof, and apair of control ports oppositely disposed with respect to the axis ofsaid power nozzle on a line intersecting therewith at a point betweensaid power nozzle and said receivers, passageway means connecting thefirst said jet receiver with one of said control ports, and passagewaymeans connecting the second said jet receiver with the other of saidcontrol ports; and B. said negative feedback means comprises said fluidamplifier, and passageway means connecting a first said output receiverto the one of said driving ports which is coupled through a reactionsurface on said jet pipe to urge said jet pipe to a position which willcause the signal from said output means to predominate in the secondsaid output receiver, and passageway means for connecting the secondsaid output receiver to the opposite of said one driving port.
 6. Thefluidic oscillator recited in claim 5 wherein said jet pipe comprises acollar flexurally mounted to said base member and having an axis ofrotation with respect thereto; a hollow pipe extending from said axis ofrotation in a direction normal thereto; and a solid member extending ina direction opposite the said one direction and including at its end thesaid reaction surfaces.
 7. The fluidic oscillator recited in claim 6wherein the axis of said jet nozzle is parallel to said axis ofrotation.